Synthesis, structure, and properties of oligo-tridentate ligands; covalently assembled precursors of coordination arrays
Oligo-tridentate ligands based on alternating pyridines and pyrimidines were synthesised by Stille-type carbon-carbon bond-forming reactions. The terpyridine-like sites are designed to coalign upon metal complexation, giving rise to organized and rigidly spaced metal ions. Peripheral functionalization of the basic bis-tridentate framework was explored. The heterocycles in the ligands are in an all-trans conformation about the interannular bonds as indicated by comparison of their 1H NMR spectra. An X-ray crystal structure analysis of the nonchiral tris-tridentate ligand 2a reveals a helical structure in the solid state. The seven heterocycles form a helical structure with resulting overlap of the terminal pyridines. Their centroid-to-centroid distance is 4.523 A with 38.8° between the planes. NMR investigations support a helical conformation in solution as well. Electrochemical and UV absorption measurements indicate that the LUMO resides on the pyrimidine moiety of the ligands.
Hanan, Garry S.,Schubert, Ulrich S.,Volkmer, Dirk,Riviere, Emmanuel,Lehn, Jean-Marie,Kyritsakas, Nathalie,Fischer, Jean
p. 169 - 182
(2007/10/03)
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